Breadth of glass transition temperature in styrene/acrylic acid block, random, and gradient copolymers: Unusual sequence distribution effects

Wong, Christopher; Kim, Jungki; Torkelson, John M.

doi:10.1002/polb.21296

Cited by 77 publications

(99 citation statements)

References 60 publications

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“…The glass transition breadth, which is another indicator of the miscibility of the blends, was determined from the derivative of the second heating curve obtained by DSC as described previously. [42][43][44][45] The determination of the T g breadth of [P 1k LA 90 CL 10 ]-[LP] 3 is illustrated in Figure 6. In the derivative heat flow curve, the onset of the glass transition is taken as crossing point from the extension lines of the baseline and the glass transition valley.…”

Section: Resultsmentioning

confidence: 99%

Blends of Paclitaxel with POSS-Based Biodegradable Polyurethanes: Morphology, Miscibility, and Specific Interactions

Guo

Knight

Wu³

et al. 2010

Macromolecules

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The morphology, miscibility, and specific interactions of paclitaxel (PTx) with a family of polyhedral oligosilsesquioxane (POSS)-based biodegradable thermoplastic polyurethanes (POSS TPUs) were investigated systematically using wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). These POSS TPUs incorporate an alternating multiblock structure formed by POSS hard segments and the soft segments composed of polylactide/caprolactone copolymer (P(DLLA-co-CL)). They feature variable poly(ethylene glycol) (PEG) content from 0 to 14 wt % through adjusting the poly(ethylene glycol) (PEG) molecular weight in P(DLLA-co-CL) soft segments of fixed molar mass of M _ n = 12 kg/mol and further to 52 wt % utilizing pure PEG M _ n = 1 kg/mol in the soft segments. Using WAXD, it was found that PTx is amorphous in all proportions in the PTx/POSS TPU blends prepared using a solutioncasting method. Interestingly, the PTx not only exhibits excellent miscibility in all of these PTx/POSS TPU blends over the whole range of the drug concentration, but also serves as an antiplasticizer by increasing the blend T g gradually from the polymer T g up to the T g of amorphous PTx. The T g -composition dependences in these blends were well fitted by the Gordon-Taylor equation. The glass transition breadth of the blends increases significantly only for drug concentrations higher than 50 wt % for most of the POSS TPUs, suggesting some spatial heterogeneity at these high drug concentrations. On the other hand, the slight increment of the blend melting temperature, T m , and latent heat, ΔH, indicates enhanced phase separation between the POSS hard segments and the TPU soft segments upon drug incorporation. Gordon-Taylor analysis and FTIR results confirm that the PEG incorporated in the POSS TPUs exhibits strong H-bonding interactions with the PTx. Although PEG can promote the favorable interactions in the PTx/POSS TPU blends, we showed that the more hydrophobic LA/CL repeat units are still required in the soft segments in order to achieve molecular-level miscibility. This systematic investigation of the PTx/POSS TPU systems may be of great value to design plasticizer/antiplasticizer for new polymer materials with controlled and tailored properties, especially for those PLA-or PCL-based biodegradable polymer systems.

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Section: Resultsmentioning

confidence: 99%

Blends of Paclitaxel with POSS-Based Biodegradable Polyurethanes: Morphology, Miscibility, and Specific Interactions

Guo

Knight

Wu³

et al. 2010

Macromolecules

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“…This was confirmed in our recent publication. 24 Because of their unique composition profiles, gradient copolymers have also been shown to exhibit an unusually broad glass transition temperature [43][44][45] (T g ) and to be effective in compatibilizing immiscible polymer blends. [46][47][48]59 The higher CMC values associated with gradient copolymers means that, on addition to an immiscible blend, gradient copolymers are less likely than block copolymers to be trapped in micelles and thus are able to affect the interfacial activity of the blend more easily than block copolymers.…”

Section: Introductionmentioning

confidence: 99%

Critical micelle concentrations of block and gradient copolymers in homopolymer: Effects of sequence distribution, composition, and molecular weight

Sandoval

Williams

Kim

et al. 2008

J Polym Sci B Polym Phys

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ABSTRACT:The critical micelle concentrations (CMCs) of styrene-methyl methacrylate (S-MMA) block and gradient copolymers present in a homopolymer poly(methyl methacrylate) (PMMA) matrix were determined using an intrinsic fluorescence technique based on the ratio of excimer to monomer fluorescence from styrene repeat units. The homopolymer molecular weight (MW) and copolymer MW, composition, and sequence distribution were varied to determine their effects on the CMC, and comparisons were made to theory. Although the effects of these parameters on micelle formation have been the focus of significant theoretical study, few experimental studies have addressed these issues. The MW of the S block (forming the micelle core) has a strong effect on the CMC. For example, an order of magnitude reduction in the CMC (from $ 1 to $ 0.1 wt %) is observed when the S block MW is increased from 51 to 147 kg/mol while maintaining the MMA block and PMMA MWs at 48-55 kg/mol. Increasing the PMMA matrix MW also has a strong an effect on the CMC, with the CMC for a nearly symmetric S-MMA block copolymer with each block MW equal to 48-51 kg/mol decreasing by a factor of 5 and by several orders of magnitude when the matrix MW is increased from 55 to 106 kg/mol and 255 kg/mol, respectively. In contrast, similar changes in the MMA block MW have little effect on the CMC. Finally, when present in a 55 kg/mol PMMA matrix, a 55 kg/mol S-MMA gradient copolymer with a styrene mole fraction of 0.51 exhibits a factor of 6 larger CMC than a block copolymer of similar MW and composition.

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“…In recent years, a number of reactions have been developed, exemplified as 'click' chemistry, which enables the efficient formation of a specific covalent linkage by addition reaction, even within a highly complex chemical environment. [47][48][49][50][51][52][53] Among these reactions, the Huisgen 1,3-dipolar cycloaddition reaction of organic azides and alkynes 54,55 has gained considerable attention due to the near quantitative yields, highly regio-selectivity, robustness, insensitivity, and most importantly, the lack of by-product formation. The triazole ring formed in the reaction is essentially chemically inert to reactive conditions, e.g.…”

Section: Cu-catalysed Azide/alkyne Click (Cuacc) Reactionmentioning

confidence: 99%

“…Polymer c-PSTY 47 -OH, 8a (0.5 g, 1.0×10 -4 mol), TEA (0.273 mL, 2.0×10 -3 mol) and 8.0 ml of dry THF were added under an argon blanket to a dry schlenk flask that has been flushed with argon.…”

Section: Synthesis Of C-psty 47 -Br 9amentioning

confidence: 99%

“…The experimental results revealed that the T g for this series of polymers was not only affected by the number of knots but also the type and location of the knots. by CuAAC of (a) PSTY 44 -≡, 4a, and (b) PSTY 44 -N 3 , 3a; (c) (PSTY 44 ) 2 15, crude, (d) (PSTY 44 ) 2 prepped and (e) LND simulation of crude, (B) c-PSTY 47 -b-PSTY 44 , 16 by CuAAC of (a) PSTY 44 by CuAAC of (a) PSTY 44 -(≡) 2 , 5a, and (b) PSTY 44 -N 3 , 3a; (c) (PSTY 44 ) 3 18, crude, (d) (PSTY 44 Table 3.1: Purity, coupling efficiency, molecular weight data (RI and triple detection) and change in hydrodynamic volume for all starting building blocks and products. ………………………… 66 There are many types of polymeric architectures that can now be made by coupling linear polymers to produce, for example, rings, grafts, branched, star-shaped, crosslinked network, and dendrimers.…”

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Synthesis of cyclic macromolecular architectures

Hossain¹

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Design and synthesis of complex polymer architectures is a promising field in polymer chemistry to produce new materials with unprecedented macroscopic properties. Recent advances in 'living' radical polymerization and polymer coupling chemistries has facilitated the fabrication of new polymer topologies. The main goal of this thesis is to develop novel methods to fabricate cyclic polymers with pendent functional groups, and use them as building blocks in the synthesis of complex polymer topologies. The 'click' reaction used to couple the cyclic polymers was by copper-catalyzed azide/alkyne cycloaddition reaction (CuAAC). The thermal properties of the resultant complex structures were investigate by Differential Scanning Calorimetry to determine the effect of topology on the glass transition temperature (T g ).First, the combination of RAFT polymerization and CuAAC reaction were used for the synthesis of cyclic polymer with pendent hydroxyl group. An alkyne functional RAFT agent was used for the synthesis of linear polystyrene (PSTY), in which the RAFT moiety was then converted to an azide moiety and a free OH group via a two step synthetic reaction.This linear polymer was cyclized in high yield and considered as a highly efficient method, and has the potential to be applied to a wide range of polymers made by RAFT. Although the monocyclic polymer was synthesized in high yield, we observed ester cleavage during the synthesis of more complex topologies from the monocyclic precursor building blocks. A detail degradation study was conducted using different catalyst/ligand complexes, and finally the methodology for the synthesis of different topologies of cyclics was amended to reduce this degradative side reaction. However, for the fabrication of more complex topologies, the synthetic methodology was redirected towards a more stable synthetic approach.A modular approach was followed for the synthesis of multifunctional linear polymer precursors through modulating the Cu(I) activity towards the click reaction over radical formation. The post-modification approach allowed for the synthesis of α, ω-heterotelechelic linear polymer precursors which was cyclised by using a modified CuAAC cyclization reaction in which the hydroxyl functional groups were equally spaced. The hydroxyl groups were converted to azides or alkynes and then further coupled together through the CuAAC reaction to produce complex structures, including a spiro tricyclic and 1 st generation dendritic structures. All these structures were produced in high yields with good 'click' efficiencies. The purity and 'click' efficiencies were calculated by fitting the experimental SEC traces with a log-normal distribution (LND) model based on fitting iii multiple Gaussiun functions for each polymer species. The crude polymer was purified by preparative SEC that essentially removes all the unreacted species and by-products.In the follow up work, a range of different topologies of cyclic homo and copolymers were synthesized by combining of ATRP, SET-LRP a...

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Breadth of glass transition temperature in styrene/acrylic acid block, random, and gradient copolymers: Unusual sequence distribution effects

Cited by 77 publications

References 60 publications

Blends of Paclitaxel with POSS-Based Biodegradable Polyurethanes: Morphology, Miscibility, and Specific Interactions

Blends of Paclitaxel with POSS-Based Biodegradable Polyurethanes: Morphology, Miscibility, and Specific Interactions

Critical micelle concentrations of block and gradient copolymers in homopolymer: Effects of sequence distribution, composition, and molecular weight

Synthesis of cyclic macromolecular architectures

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